Re: 57yrs old and never had the FLU shot! Gotta have one now!
I see that you have probably either gotten your flu shot already or chose to reject it.
But just to reiterate what others have said, the flu shot will not cause the flu. It is possible to have a few symptoms after the injection such as runny nose that may resemble the flu or a cold, and pain in the arm is also common since it is given into the muscle.
You may get the flu shot at any time and it is recommended that it be repeated every year.
The idea of getting the flu shot is to protect you against strains of influenza. Influenza is common, but for some individuals they are at a higher risk to have serious complications or even suffer from death.
I am unsure what your job is, but if you are around other individuals then it is important for you to be vaccinated against the flu. This will protect you as well as the individuals you come into contact with from getting influenza.
The idea is that if most individuals get their vaccinations then in general there may be a decrease in the number of flu cases that arise.
If you are around anyone who has a weakened immune system, is pregnant, or has other medical conditions then it is important to get your vaccination to help protect them from developing the flu.